U.S. patent application number 10/937737 was filed with the patent office on 2006-03-09 for healing algorithm.
This patent application is currently assigned to Micronic Laser Systems AB. Invention is credited to Lars Ivansen.
Application Number | 20060053406 10/937737 |
Document ID | / |
Family ID | 35198025 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060053406 |
Kind Code |
A1 |
Ivansen; Lars |
March 9, 2006 |
Healing algorithm
Abstract
An aspect of the present invention includes a method for
reshaping sub-objects in at least one object in pattern design data
to be presented to a mask writer or a direct writer for producing a
pattern onto a workpiece, where said object comprises a plurality
of slivers in a first direction, comprising the actions of: a)
generating a list of slivers, repeating the actions of: b)
comparing a dynamic object in an object list with the slivers in
said list of slivers to look for adjacent slivers, c) removing
adjacent slivers from said list of slivers to said object list, d)
merging adjacent slivers with said dynamic object, e) terminating
the repetition when no slivers in said list of slivers are adjacent
to said dynamic object in said object list. Other aspects of the
present invention are reflected in the detailed description,
figures and claims.
Inventors: |
Ivansen; Lars; (Solna,
SE) |
Correspondence
Address: |
HAYNES BEFFEL & WOLFELD LLP
P O BOX 366
HALF MOON BAY
CA
94019
US
|
Assignee: |
Micronic Laser Systems AB
Taby
SE
|
Family ID: |
35198025 |
Appl. No.: |
10/937737 |
Filed: |
September 9, 2004 |
Current U.S.
Class: |
716/55 |
Current CPC
Class: |
G03F 7/70383 20130101;
G03F 7/70508 20130101; G03F 7/70291 20130101; G03F 7/70433
20130101 |
Class at
Publication: |
716/020 ;
716/021 |
International
Class: |
G06F 17/50 20060101
G06F017/50 |
Claims
1. A method for reshaping sub-objects in at least one object in
pattern design data to be presented to a mask writer or a direct
writer for producing a pattern onto a workpiece, where said object
comprises a plurality of slivers in a first direction, comprising
the actions of: a) generating a list of slivers, repeating the
actions of: b) comparing a dynamic object in an object list with
the slivers in said list of slivers to look for adjacent slivers,
c) removing adjacent slivers from said list of slivers to said
object list, d) merging adjacent slivers with said dynamic object,
e) terminating the repetition when no slivers in said list of
slivers are adjacent to said dynamic object in said object
list.
2. The method according to claim 1, further comprising the action
of refracturing said dynamic object at least in a direction
perpendicular to said first direction.
3. The method according to claim 1, wherein said dynamic object is
compared both on its lower and upper long side with an upper and
lower long side respectively of each sliver in said list of
slivers.
4. The method according to claim 1, wherein said dynamic object
originally is a sliver.
5. The method according to claim 1, wherein said sliver is defined
by its aspect ration, which is equal to or smaller than 1:3.
6. The method according to claim 2, wherein said refracturing
divides said dynamic object into rectangles or trapezoids.
7. The method according to claim 1, wherein said workpiece is a
semi conducting substrate.
8. The method according to claim 1, wherein said workpiece is a
mask or reticle substrate.
9. The method according to claim 1, wherein said mask writer or
maskless writer is based on a SLM for generating the pattern on
said workpiece.
10. The method according to claim 1, wherein said mask writer or
maskless writer is a raster type mask writer or maskless
writer.
11. The method according to claim 1, wherein said list of slivers
comprising a smaller amount of slivers than the full amount of
slivers in said pattern design data.
12. The method according to claim 1, wherein said reshaping of said
sub-objects comprising the action of: minimizing a circumference of
at least one object in said pattern design data.
13. The method according to claim 1, wherein said mask writer or
maskless writer is of VSB type.
Description
TECHNICAL FIELD
[0001] The present invention relates to an improved data processing
method in lithography for reducing the overall writing time, in
particular it relates to an improved method of healing geometry
data for mask or maskless lithography.
BACKGROUND OF THE INVENTION
[0002] Over time, chips have become increasingly complex and dense,
as processors, memory circuits and other semi-conductors have
gained greater capacity. Memory circuits, in particular, and all
circuits with small features, in general, have become denser.
Patterns for these circuits have become even more complex than the
circuits, as optical proximity and laser proximity correction
features have been added to the patterns. The equipment and writing
strategies have become increasingly sophisticated, in response to
requirements for smaller features on chips and tighter critical
dimensions.
[0003] A considerable amount of design data to be presented to a
pattern generator, for instance a mask writer or a direct writer
(maskless writer) is heavily slivered. A great deal of
object/feature in design data, for instance CIF.TM., OASIS.TM.,
Applicon.TM., DXF.TM., MEBES.TM. or GDS-II.TM.), is divided into
several sub objects/features: These sub objects/features are
created because said object/features comprise numerous jogs
defining optical proximity and laser proximity corrections. A sub
object/feature with a certain aspect ratio is defined as a sliver.
Slivers make the processing of design data more, for not saying
extremely, compute intensive and for the time being there are no
mask writers or maskless writers, which benefit from the appearance
of said slivers, yet said slivers are generated. A certain feature
with a plurality of slivers will in total have an unnecessary large
circumference, as all slivers are treated as an object to be
printed. Treating numerous slivers will increase the total writing
time for a raster pattern generator, for instance Micronic
Sigma7300 or Micronic Omega6600, which is a problem. For a Vector
shape beam pattern generator, for instance JEOL JBX-3030MV, there
is also a problem with slivers since too narrow slivers will create
CD (critical dimension) variations. If the slivers become small
enough they are impossible to write with VSB pattern
generators.
[0004] As manufacturers strive to keep pace with the Moor's law,
there is a continuing need for writers that can process large
volumes of geometric figures, i.e., object features in design data,
and produce precise patterns on work pieces. There is a need in the
art to reduce the writing time while producing the needed precise
pattern.
SUMMARY OF THE INVENTION
[0005] An aspect of the present invention includes a method for
minimizing a circumference of at least one object in pattern data
to be presented to a mask writer or a direct writer, where said
object comprises a plurality of slivers in a first direction,
comprising the actions of: a) generating a list of slivers, b)
comparing a dynamic object in an object list with the slivers in
said list of slivers to look for adjacent slivers, c) removing
adjacent slivers from said list of slivers to said object list, d)
merging adjacent slivers with said dynamic object, e) repeating
action b-d until no slivers in said list of slivers is adjacent to
said dynamic object in said object list.
[0006] Other aspects of the present invention are reflected in the
detailed description, figures and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] FIG. 1a depicts a design data feature as presented to a mask
writer or a maskless writer.
[0008] FIG. 1b depicts the feature in FIG. 1a after healing.
[0009] FIG. 1c depicts the feature as illustrated in FIG. 1b after
refracturing.
[0010] FIG. 2 depicts one embodiment of a healing method according
to the present invention.
[0011] FIG. 3 depicts a simplified SLM mask- or mask-less
writer.
[0012] FIG. 4 depicts a schematic flowchart from design data to the
patterning step in a lithographic raster pattern generator.
DETAILED DESCRIPTION
[0013] The following detailed description is made with reference to
the figures. Preferred embodiments are described to illustrate the
present invention, not to limit its scope, which is defined by the
claims. Those of ordinary skill in the art will recognize a variety
of equivalent variations on the description that follows.
[0014] FIG. 3 illustrates an embodiment of an apparatus for
patterning a work piece 60 according to prior art, which may
benefit of the present invention.
[0015] Said apparatus comprising a source 10 for emitting
electromagnetic radiation, an objective lens arrangement 50, a
computer-controlled reticle 30, a beam conditioning arrangement 20,
a spatial filter 70 in a Fourier plane, a Fourier lens arrangement
40 and said work piece 60.
[0016] The source 10 may emit radiation in the range of wavelengths
from infrared (IR), which is defined as 780 nm up to about 20
.mu.m, to extreme ultraviolet (EUV), which in this application is
defined as the range from 100 nm and down as far as the radiation
is possible to be treated as electromagnetic radiation, i.e.
reflected and focused by optical components. The source 10 emits
radiation either pulsed or continuously. The emitted radiation from
the continuous radiation source 10 can be formed into a pulsed
radiation by means of a shutter located in the radiation path
between said radiation source 10 and said computer-controlled
reticle 30. For example, the radiation source may be a KrF excimer
laser with a pulsed output at 248 nm, a pulse length of
approximately 10 ns and a repetition rate of 1000 Hz. The
repetition rate may be below or above 1000 Hz.
[0017] The beam conditioning arrangement 20 may be a simple lens or
an assembly of lenses. The beam conditioning arrangement 20
distributes the radiation emitted from the radiation source 10
uniformly over a surface of the computer-controlled reticle 30. In
case of a continuous radiation source a beam of such a source may
be scanned over the surface of the computer-controlled reticle.
[0018] Workpiece 60 is moved in a systematic fashion so that the
optical system synthesizes the desired device layer pattern.
[0019] The computer-controlled reticle 30 may be a Spatial Light
Modulator (SLM). In this embodiment the SLM comprises all
information at a single moment that is required to pattern a
certain area of the workpiece 60.
[0020] For the remainder of this application an electrostatically
controlled micro mirror matrix (one- or two dimensional) is
assumed, although other arrangements as described above are
possible, such as transmissive or reflective SLMs relying on LCD
crystals or electrooptical materials as their modulation mechanism,
or micromechanical SLMs using piezoelectric or electrostrictive
actuation.
[0021] The SLM 30 is a programmable device that produces an output
radiation beam that is modulated by separate inputs from a
computer. The SLM 30 simulates the function of a mask through the
generation of bright and dark pixels in response to computer fed
data. For example the phase SLM 30 is an array of etched solid
state mirrors. Each micromirror element is suspended above a
silicon substrate by restoring hinges, which may be supported
either by separate support posts or by the adjacent mirrors.
Beneath the micromirror element are address electrodes. One
micromirror represents one pixel in the object plane. The pixel in
the image plane is here defined as to have the same geometry as the
micromirror but the size may be different due to the optics, i.e.
larger or smaller depending on whether the optics is magnifying or
demagnifying.
[0022] The micromirror and the address electrodes act as a
capacitor so that for example a negative voltage applied to the
micromirror, along with a positive voltage to the address
electrode, will twist the torsion hinges suspending the micromirror
which in turn allow the micromirror to rotate or to move up or
down, thereby creating a phase modulation of the reflected
light.
[0023] A projection system comprises in this embodiment the Fourier
lens arrangement 40, which may be a compounded tube lens, the
spatial filter 70 and the objective lens arrangement 50. The
Fourier lens arrangement 40 and the spatial filter 70 form together
what is generally called a Fourier filter. The Fourier lens
arrangement 40 projects the diffraction pattern onto the spatial
filter 70. The objective lens arrangement 50, which may be a
compounded final lens, forms the aerial image on the work piece
60.
[0024] The spatial filter 70 is in this embodiment an aperture in a
plate. Said aperture being sized and positioned so as to block out
essentially all light which is diffracted into the first and higher
diffraction orders, for example said aperture may be located at the
focal distance from the Fourier lens arrangement 40. The reflected
radiation is collected by said Fourier lens arrangement 40 in the
focal plane, which acts at the same time as a pupil plane of the
objective lens arrangement 50. The aperture cuts out the light from
the first and higher diffraction orders of the addressed
micromirrors in the SLM, while the radiation from the non-addressed
mirror surfaces can pass the aperture. The result is an intensity
modulated aerial image on the work piece 60 as in conventional
lithography.
[0025] FIG. 4 depicts a schematic flowchart from design data to a
patterning step in a lithographic pattern generator, i.e., a mask
writer or a mask less writer. A first step indicates the pattern
design raw data, which may come from CIF.TM., Applicon.TM.,
DXF.TM., MEBES.TM., OASIS.TM. or GDS-II.TM.. Said design data needs
to be preprocessed in the pre process step 420 in order to fit the
pattern generator which is going to pattern said design data onto a
workpiece, for instance a mask substrate or a semiconducting
substrate. Said preprocess step may comprise the inventive method.
In a rasterizer 430 said design data is rasterized into a pixel
pattern. Said pixel pattern is preferably finer than the pixels of
the pattern generator. In a SLM based pattern generator said pixels
are micromirrors of a certain size, for instance a rectangle with a
side being 16 .mu.m. Such a size of a micromirror together with a
demagnification of 200 times means a pixel size on said workpiece,
which is 80 nm. Allowing each SLM pixel to be set in 65 different
gray level states said pixel size on said workpiece decreases to
1.25 nm. The pixel size in said rasterized design data may be in
the same order of magnitude or smaller as said pixel size of said
SLM onto the workpiece. Said rasterized design data, now in pixel
form, is thereafter transferred into drive signals for the
micromirrors in said SLM.
[0026] Instead of using an SLM as a modulator for generating the
pattern on said workpiece other types of lithographic methods may
be used such as acousto optical modulator in combination with an
acousto optical deflector, which is used in Mironic's pattern
generator denoted Omega6600. Instead of using laser as the source
for exposing a resist layer onto of said workpiece an electron beam
source may be used according to well known techniques in the art
and therefore needs no further clarification in this
disclosure.
[0027] In a final patterning step 450 said SLM is loaded with the
intended pattern and a laser pulse is impinged onto said SLM and
relayed onto said workpiece where a layer sensitive to the
wavelength used is exposed according to the pattern design
data.
[0028] FIG. 1a illustrates an object/feature 100 comprising
numerous sub features/objects 110, 111, 112, 113, 114, 115, 116,
117 118, 119, 120, 122, 124, 126, 128, 130. The object/feature 100
illustrated in FIG. 1a is a typical example of how design data may
look like as generated from a data format like CIF.TM.,
Applicon.TM., DXF.TM., MEBES.TM., OASIS.TM. or GDS-II.TM.. The sub
features/objects 110, 111, 112, 113, 114, 115, 116, 117 118, 119,
120, 122, 124, 126, 128, 130 are generated for each and every jog
in y-direction. Some of said sub features/objects have an aspect
ratio defining a sliver 110, 111, 112, 113, 114, 115, 116, 117,
118, 119. A sliver is a sub feature/object, which is much longer in
a first direction, in FIG. 1a X-direction, compared to its
perpendicular direction, in FIG. 1a Y-direction. The aspect ratio
defining a sliver may vary, but a ratio of 1:10 may be a typical
example of a sliver. When the aspect ratio is bigger than 1:3,
i.e., 1:2 or 1:1 one is normally not talking about a sliver,
whereas an aspect ratio equal or smaller than 1:3, i.e., 1:4, 1:5,
1:6 etc one is normally talking about a sliver.
[0029] In FIG. 1a sub objects 120, 112, 124, 126, 128, 130 are not
treated as slivers as their aspect ratio is too large.
[0030] As can be seen from FIG. 1a, said object/feature 100 has a
large feature outline or circumference when said slivers 110, 111,
112, 113, 114, 115, 116, 117, 118, 119 and other sub
objects/features 120, 122, 124, 126, 128, 130 are taken into
account, which is unnecessarily compute intensive for the pattern
generator to handle. The reason why this slivered objects/features
is so compute intensive is that each sliver is treated as an
individual object, although many slivers belong to the same object
to be printed, here in FIG. 1a said slivers 110, 112, 113, 114,
115, 116, 117, 118, 119 belong to feature 100.
[0031] FIG. 1b illustrates the same object/feature 100 as
illustrated in FIG. 1a, but here with all slivers healed according
to an embodiment of the present invention. It is clear by just
comparing FIGS. 1a and 1b with each other that the total feature
outline or circumference is much smaller in FIG. 1b compared to
FIG. 1a. It will take much less time to process sub object 150
together with sub objects 120, 122, 124, 126, 128 and 130 compared
to sub objects 120, 122, 124, 126, 128, 130 and each and every
sliver 110, 111, 112, 113, 114, 115, 116, 117, 118, 119.
[0032] FIG. 1c illustrates the same object/feature 100 as
illustrated in FIG. 1b, but here after refracturing the sub object
150 in FIG. 1b. The original design data of feature/object 100 as
illustrated in FIG. 1a had slivers extending in X-direction. For
not recreating said slivers extending in X-direction said
refracturing is performed in Y direction instead of X-direction,
i.e., +/-90 degrees rotation of data. By doing so the original
slivers are not recreated. Instead new sub objects/features are
created denoted by 170, 171, 172, 173, 174, 175, 176, 177, 178,
179, 180. Sub object 190 is a rectangle as is true for all other
sub objects/features in FIG. 1c. Sub objects features 120, 122,
124, 126, 128, 130 are not changed during the healing process or
the refracturing process.
[0033] FIG. 2 illustrates a flow chart of one embodiment of the
healing method according to the present invention. Objects/features
are read from the design data storage 210. All objects/features are
checked if said objects/features are slivers or not 220, which is
determined by an aspect ratio to be defined, for instance smaller
than 1:3. If said object/feature is not a sliver then bypass 230
said object/feature from the healing method and check a next
object/feature from the design data storage 210. In FIG. 1a sub
features/objects 120, 122, 124, 126, 128, 130 are bypassed from the
healing method because of their aspect ratio.
[0034] If said object/feature is a sliver then store said sliver in
a list of slivers 240. In one embodiment according to the present
invention said list of slivers may contain all slivers in the
design data storage 210. In another embodiment said list of slivers
only comprises a limited number of the total amount of slivers in
said design data storage 210. Healing of design data, in the most
general form, is a compute intensive task where each and every one
of the slivers is tested for absolute proximity towards all other
slivers in a population of the design data. Such a test becomes
quickly insurmountable with the vast object/feature count in
semiconductor design.
[0035] By narrowing down the task to suppress the occurrences of
slivers, one could rely on the assumption that slivers are
generated in a pseudo systematic way, spatial proximity tends to
have a correspondence in design data. A sliver typically has its
neighbors located close in the design data storage. By leveraging
this observation, a healing algorithm could be narrowed down to
span only a window of object/feature candidates, and hence reduce
the number of conditional test to a manageable level.
[0036] A list of slivers 240 holds slivers that are scanned for
matching towards a current dynamic object in an object list 290.
The size of the list of slivers is a tuning parameter, as could
easily be understood from the description above, which has to be
defined at a start up event. A larger list of slivers improves the
probability of matching slivers into said dynamic object, but also
increases the computer load. A smaller list may miss some of the
matchmaking, but will execute more efficiently. The ideal balance
must be determined by benchmarking production patterns.
[0037] The object list holds the dynamic object that is currently
being generated. The size of the list is dynamic and grows with the
number of slivers that are found to match. This could easily be
understood since the more slivers that are joined or healed
together into said dynamic object the more space is required to
store said dynamic object, and the size of said space is depending
on the number of successful matches. However, a maximum size of the
list could be applied to keep it within manageable numbers.
[0038] In the embodiment where the number of slivers checked were
less than the total number of slivers, there is a check when
loading said list of slivers if said list is full or not 235. One
of the slivers in said list of slivers is then transferred from
said list to said list of objects 290, alternatively a completely
new sliver from the design data storage 210 is transferred directly
to the list of objects 290. Said sliver in said list of objects 290
is compared with the slivers in said list of slivers 240. Here one
is comparing if one or a plurality of the slivers in said list of
slivers is adjacent to the dynamic object in the list of objects
290. An upper long side of said dynamic object is compared to a
lower long side of said slivers 110, 111, 112, 113, 114, 115, 116,
117, 118, 119 and a lower long side of said dynamic object is
compared to an upper long side of said slivers 110, 111, 112, 113,
114, 115, 116, 117, 118, 119. Said upper or lower long side of said
dynamic object is dynamically changing after merging with one or a
plurality of said slivers.
[0039] The match making of slivers that are adjacent could be
accelerated by limiting the test to exact matches of coordinates
and along one axis only (the long side of the sliver). If said
sliver for some reason are adjacent on the narrow side, those cases
could be considered unusual and disregarded. An initial test only
uses the Y-coordinate, looking for an exact match. If they match,
the X intervals of the two slivers are checked for coincidence. By
limiting the initial matchmaking to one axis dramatically reduces
the number of tests and simplifies the structure in which the
dynamic object are stored, i.e., the list could be sorted on
y-coordinates in the first dimension and X-coordinates in a second
dimension.
[0040] The test for slivers 220 is there for two reasons. Firstly,
it suppresses unnecessary processing for geometries that issue no
particular problem downstream in the data processing. Secondly, it
sorts out features/objects that have an extent in one particular
direction. The later is required for a fracturing to work in an
optimal way.
[0041] In said dynamic object said slivers are healed or merged
together by removing internal boarder lines, which originally
divide one sliver from another sliver. Only the outer boarder line
of the dynamic object, defining its shape, is left unchanged. The
healed object may have any shape of a polygon.
[0042] In one embodiment according to the present invention said
healed data is refractured. Said refracturing is made because the
data processing in the pattern generator only accepts pattern data
comprising rectangles and trapezoids. In a case where said pattern
generator accepts monotonous polygons, a refracturing may be
required depending on the shape of the polygon. This step is
unnecessary if the pattern generator is accepting any shape of
polygons. The refracturing works by dividing a healed polygon at
each vertex in the Y-direction. For polygons which originally have
slivers in X-direction, the refracturing would cut the resulting
polygon in y, in FIG. 1c sub features/objects 170, 171, 172, 173,
174, 175, 176, 177, 178, 179 and 180 are sub objects/features that
are created after refracturing. The test for slivers in the healing
algorithm provides control over the general extent of the polygon,
information that is now applied in the refracturing. There are of
course no fundamental limitations on to which axis the healing
algorithm is applied. If the pattern data requires rotation for
throughput reasons, the conditions could be rotated as well. The
sliver test could even be extended to include both X- and Y-sliver
detection, which would serve the benefit that all slivers could be
healed, regardless of orientation and hence the algorithm would be
neutral to rotation. The output from the sliver test would feed two
separate channels, each representing a sliver orientation.
[0043] Given a pattern comprising slivers it is possible to
accomplish healing by the inventive method that may decrease the
summarized circumference for all rectangles in a pattern with a
factor 0.3. For a raster pattern generator said decrease in
circumference of features to be written will most likely decrease
the writing time. For VSB pattern generators said decrease in
circumference, and hence optimized X/Y ratio, will lead to a better
CD control.
[0044] A processing time of the healing can be as low as the
reading time of the pattern from the pattern data storage 210 into
the pattern generator. The overhead of healing is low, meaning that
if no slivers are detected, there is no, or very little, increase
in processing time.
[0045] While the preceding examples are cast in terms of a method,
devices and systems employing this method are easily understood. A
magnetic memory containing a program capable of practicing the
claimed method is one such device. A computer system having memory
loaded with a program practicing the claimed method is another such
device.
[0046] While the present invention is disclosed by reference to the
preferred embodiments and examples detailed above, it is understood
that these examples are intended in an illustrative rather than in
a limiting sense. It is contemplated that modifications and
combinations will readily occur to those skilled in the art, which
modifications and combinations will be within the spirit of the
invention and the scope of the following claims.
* * * * *